<?php
/*
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * This software consists of voluntary contributions made by many individuals
 * and is licensed under the LGPL. For more information, see
 * <http://www.doctrine-project.org>.
 */

namespace Doctrine\ORM;

use Doctrine\ORM\Query\Expr;

/**
 * This class is responsible for building DQL query strings via an object oriented
 * PHP interface.
 *
 * @since 2.0
 * @author Guilherme Blanco <guilhermeblanco@hotmail.com>
 * @author Jonathan Wage <jonwage@gmail.com>
 * @author Roman Borschel <roman@code-factory.org>
 */
class QueryBuilder {
	/* The query types. */
	const SELECT = 0;
	const DELETE = 1;
	const UPDATE = 2;
	
	/** The builder states. */
	const STATE_DIRTY = 0;
	const STATE_CLEAN = 1;
	
	/**
	 * @var EntityManager The EntityManager used by this QueryBuilder.
	 */
	private $_em;
	
	/**
	 * @var array The array of DQL parts collected.
	 */
	private $_dqlParts = array( 'select' => array(), 'from' => array(), 'join' => array(), 'set' => array(), 'where' => null, 'groupBy' => array(), 'having' => null, 'orderBy' => array() );
	
	/**
	 * @var integer The type of query this is. Can be select, update or delete.
	 */
	private $_type = self::SELECT;
	
	/**
	 * @var integer The state of the query object. Can be dirty or clean.
	 */
	private $_state = self::STATE_CLEAN;
	
	/**
	 * @var string The complete DQL string for this query.
	 */
	private $_dql;
	
	/**
	 * @var array The query parameters.
	 */
	private $_params = array();
	
	/**
	 * @var array The parameter type map of this query.
	 */
	private $_paramTypes = array();
	
	/**
	 * @var integer The index of the first result to retrieve.
	 */
	private $_firstResult = null;
	
	/**
	 * @var integer The maximum number of results to retrieve.
	 */
	private $_maxResults = null;
	
	/**
	 * Initializes a new <tt>QueryBuilder</tt> that uses the given <tt>EntityManager</tt>.
	 * 
	 * @param EntityManager $em The EntityManager to use.
	 */
	public function __construct(EntityManager $em) {
		$this->_em = $em;
	}
	
	/**
	 * Gets an ExpressionBuilder used for object-oriented construction of query expressions.
	 * This producer method is intended for convenient inline usage. Example:
	 *
	 * <code>
	 * $qb = $em->createQueryBuilder()
	 * ->select('u')
	 * ->from('User', 'u')
	 * ->where($qb->expr()->eq('u.id', 1));
	 * </code>
	 *
	 * For more complex expression construction, consider storing the expression
	 * builder object in a local variable.
	 *
	 * @return Expr
	 */
	public function expr() {
		return $this->_em->getExpressionBuilder();
	}
	
	/**
	 * Get the type of the currently built query.
	 *
	 * @return integer
	 */
	public function getType() {
		return $this->_type;
	}
	
	/**
	 * Get the associated EntityManager for this query builder.
	 *
	 * @return EntityManager
	 */
	public function getEntityManager() {
		return $this->_em;
	}
	
	/**
	 * Get the state of this query builder instance.
	 *
	 * @return integer Either QueryBuilder::STATE_DIRTY or QueryBuilder::STATE_CLEAN.
	 */
	public function getState() {
		return $this->_state;
	}
	
	/**
	 * Get the complete DQL string formed by the current specifications of this QueryBuilder.
	 *
	 * <code>
	 * $qb = $em->createQueryBuilder()
	 * ->select('u')
	 * ->from('User', 'u')
	 * echo $qb->getDql(); // SELECT u FROM User u
	 * </code>
	 *
	 * @return string The DQL query string.
	 */
	public function getDQL() {
		if( $this->_dql !== null && $this->_state === self::STATE_CLEAN ) {
			return $this->_dql;
		}
		
		$dql = '';
		
		switch ( $this->_type ) {
			case self::DELETE :
				$dql = $this->_getDQLForDelete();
				break;
			
			case self::UPDATE :
				$dql = $this->_getDQLForUpdate();
				break;
			
			case self::SELECT :
			default :
				$dql = $this->_getDQLForSelect();
				break;
		}
		
		$this->_state = self::STATE_CLEAN;
		$this->_dql = $dql;
		
		return $dql;
	}
	
	/**
	 * Constructs a Query instance from the current specifications of the builder.
	 *
	 * <code>
	 * $qb = $em->createQueryBuilder()
	 * ->select('u')
	 * ->from('User', 'u');
	 * $q = $qb->getQuery();
	 * $results = $q->execute();
	 * </code>
	 *
	 * @return Query
	 */
	public function getQuery() {
		return $this->_em->createQuery( $this->getDQL() )->setParameters( $this->_params, $this->_paramTypes )->setFirstResult( $this->_firstResult )->setMaxResults( $this->_maxResults );
	}
	
	/**
	 * Gets the root alias of the query. This is the first entity alias involved
	 * in the construction of the query.
	 *
	 * <code>
	 * $qb = $em->createQueryBuilder()
	 * ->select('u')
	 * ->from('User', 'u');
	 *
	 * echo $qb->getRootAlias(); // u
	 * </code>
	 *
	 * @return string $rootAlias
	 * @todo Rename/Refactor: getRootAliases(), there can be multiple roots!
	 */
	public function getRootAlias() {
		return $this->_dqlParts['from'][0]->getAlias();
	}
	
	/**
	 * Sets a query parameter for the query being constructed.
	 *
	 * <code>
	 * $qb = $em->createQueryBuilder()
	 * ->select('u')
	 * ->from('User', 'u')
	 * ->where('u.id = :user_id')
	 * ->setParameter(':user_id', 1);
	 * </code>
	 *
	 * @param string|integer $key The parameter position or name.
	 * @param mixed $value The parameter value.
	 * @param string|null $type PDO::PARAM_* or \Doctrine\DBAL\Types\Type::* constant
	 * @return QueryBuilder This QueryBuilder instance.
	 */
	public function setParameter($key, $value, $type = null) {
		if( $type !== null ) {
			$this->_paramTypes[$key] = $type;
		}
		$this->_params[$key] = $value;
		return $this;
	}
	
	/**
	 * Sets a collection of query parameters for the query being constructed.
	 *
	 * <code>
	 * $qb = $em->createQueryBuilder()
	 * ->select('u')
	 * ->from('User', 'u')
	 * ->where('u.id = :user_id1 OR u.id = :user_id2')
	 * ->setParameters(array(
	 * ':user_id1' => 1,
	 * ':user_id2' => 2
	 * ));
	 * </code>
	 *
	 * @param array $params The query parameters to set.
	 * @return QueryBuilder This QueryBuilder instance.
	 */
	public function setParameters(array $params, array $types = array()) {
		$this->_paramTypes = $types;
		$this->_params = $params;
		return $this;
	}
	
	/**
	 * Gets all defined query parameters for the query being constructed.
	 *
	 * @return array The currently defined query parameters.
	 */
	public function getParameters() {
		return $this->_params;
	}
	
	/**
	 * Gets a (previously set) query parameter of the query being constructed.
	 * 
	 * @param mixed $key The key (index or name) of the bound parameter.
	 * @return mixed The value of the bound parameter.
	 */
	public function getParameter($key) {
		return isset( $this->_params[$key] ) ? $this->_params[$key] : null;
	}
	
	/**
	 * Sets the position of the first result to retrieve (the "offset").
	 *
	 * @param integer $firstResult The first result to return.
	 * @return QueryBuilder This QueryBuilder instance.
	 */
	public function setFirstResult($firstResult) {
		$this->_firstResult = $firstResult;
		return $this;
	}
	
	/**
	 * Gets the position of the first result the query object was set to retrieve (the "offset").
	 * Returns NULL if {@link setFirstResult} was not applied to this QueryBuilder.
	 * 
	 * @return integer The position of the first result.
	 */
	public function getFirstResult() {
		return $this->_firstResult;
	}
	
	/**
	 * Sets the maximum number of results to retrieve (the "limit").
	 * 
	 * @param integer $maxResults The maximum number of results to retrieve.
	 * @return QueryBuilder This QueryBuilder instance.
	 */
	public function setMaxResults($maxResults) {
		$this->_maxResults = $maxResults;
		return $this;
	}
	
	/**
	 * Gets the maximum number of results the query object was set to retrieve (the "limit").
	 * Returns NULL if {@link setMaxResults} was not applied to this query builder.
	 * 
	 * @return integer Maximum number of results.
	 */
	public function getMaxResults() {
		return $this->_maxResults;
	}
	
	/**
	 * Either appends to or replaces a single, generic query part.
	 *
	 * The available parts are: 'select', 'from', 'join', 'set', 'where',
	 * 'groupBy', 'having' and 'orderBy'.
	 *
	 * @param string $dqlPartName 
	 * @param string $dqlPart 
	 * @param string $append 
	 * @return QueryBuilder This QueryBuilder instance.
	 */
	public function add($dqlPartName, $dqlPart, $append = false) {
		$isMultiple = is_array( $this->_dqlParts[$dqlPartName] );
		
		if( $append && $isMultiple ) {
			$this->_dqlParts[$dqlPartName][] = $dqlPart;
		} else {
			$this->_dqlParts[$dqlPartName] = ($isMultiple) ? array( $dqlPart ) : $dqlPart;
		}
		
		$this->_state = self::STATE_DIRTY;
		
		return $this;
	}
	
	/**
	 * Specifies an item that is to be returned in the query result.
	 * Replaces any previously specified selections, if any.
	 *
	 * <code>
	 * $qb = $em->createQueryBuilder()
	 * ->select('u', 'p')
	 * ->from('User', 'u')
	 * ->leftJoin('u.Phonenumbers', 'p');
	 * </code>
	 *
	 * @param mixed $select The selection expressions.
	 * @return QueryBuilder This QueryBuilder instance.
	 */
	public function select($select = null) {
		$this->_type = self::SELECT;
		
		if( empty( $select ) ) {
			return $this;
		}
		
		$selects = is_array( $select ) ? $select : func_get_args();
		
		return $this->add( 'select', new Expr\Select( $selects ), false );
	}
	
	/**
	 * Adds an item that is to be returned in the query result.
	 *
	 * <code>
	 * $qb = $em->createQueryBuilder()
	 * ->select('u')
	 * ->addSelect('p')
	 * ->from('User', 'u')
	 * ->leftJoin('u.Phonenumbers', 'p');
	 * </code>
	 *
	 * @param mixed $select The selection expression.
	 * @return QueryBuilder This QueryBuilder instance.
	 */
	public function addSelect($select = null) {
		$this->_type = self::SELECT;
		
		if( empty( $select ) ) {
			return $this;
		}
		
		$selects = is_array( $select ) ? $select : func_get_args();
		
		return $this->add( 'select', new Expr\Select( $selects ), true );
	}
	
	/**
	 * Turns the query being built into a bulk delete query that ranges over
	 * a certain entity type.
	 *
	 * <code>
	 * $qb = $em->createQueryBuilder()
	 * ->delete('User', 'u')
	 * ->where('u.id = :user_id');
	 * ->setParameter(':user_id', 1);
	 * </code>
	 *
	 * @param string $delete The class/type whose instances are subject to the deletion.
	 * @param string $alias The class/type alias used in the constructed query.
	 * @return QueryBuilder This QueryBuilder instance.
	 */
	public function delete($delete = null, $alias = null) {
		$this->_type = self::DELETE;
		
		if( !$delete ) {
			return $this;
		}
		
		return $this->add( 'from', new Expr\From( $delete, $alias ) );
	}
	
	/**
	 * Turns the query being built into a bulk update query that ranges over
	 * a certain entity type.
	 *
	 * <code>
	 * $qb = $em->createQueryBuilder()
	 * ->update('User', 'u')
	 * ->set('u.password', md5('password'))
	 * ->where('u.id = ?');
	 * </code>
	 *
	 * @param string $update The class/type whose instances are subject to the update.
	 * @param string $alias The class/type alias used in the constructed query.
	 * @return QueryBuilder This QueryBuilder instance.
	 */
	public function update($update = null, $alias = null) {
		$this->_type = self::UPDATE;
		
		if( !$update ) {
			return $this;
		}
		
		return $this->add( 'from', new Expr\From( $update, $alias ) );
	}
	
	/**
	 * Create and add a query root corresponding to the entity identified by the given alias,
	 * forming a cartesian product with any existing query roots.
	 *
	 * <code>
	 * $qb = $em->createQueryBuilder()
	 * ->select('u')
	 * ->from('User', 'u')
	 * </code>
	 *
	 * @param string $from   The class name.
	 * @param string $alias  The alias of the class.
	 * @return QueryBuilder This QueryBuilder instance.
	 */
	public function from($from, $alias) {
		return $this->add( 'from', new Expr\From( $from, $alias ), true );
	}
	
	/**
	 * Creates and adds a join over an entity association to the query.
	 *
	 * The entities in the joined association will be fetched as part of the query
	 * result if the alias used for the joined association is placed in the select
	 * expressions.
	 *
	 * <code>
	 * $qb = $em->createQueryBuilder()
	 * ->select('u')
	 * ->from('User', 'u')
	 * ->join('u.Phonenumbers', 'p', Expr\Join::WITH, 'p.is_primary = 1');
	 * </code>
	 *
	 * @param string $join The relationship to join
	 * @param string $alias The alias of the join
	 * @param string $conditionType The condition type constant. Either ON or WITH.
	 * @param string $condition The condition for the join
	 * @return QueryBuilder This QueryBuilder instance.
	 */
	public function join($join, $alias, $conditionType = null, $condition = null) {
		return $this->innerJoin( $join, $alias, $conditionType, $condition );
	}
	
	/**
	 * Creates and adds a join over an entity association to the query.
	 * 
	 * The entities in the joined association will be fetched as part of the query
	 * result if the alias used for the joined association is placed in the select
	 * expressions.
	 *
	 * [php]
	 * $qb = $em->createQueryBuilder()
	 * ->select('u')
	 * ->from('User', 'u')
	 * ->innerJoin('u.Phonenumbers', 'p', Expr\Join::WITH, 'p.is_primary = 1');
	 *
	 * @param string $join The relationship to join
	 * @param string $alias The alias of the join
	 * @param string $conditionType The condition type constant. Either ON or WITH.
	 * @param string $condition The condition for the join
	 * @return QueryBuilder This QueryBuilder instance.
	 */
	public function innerJoin($join, $alias, $conditionType = null, $condition = null) {
		return $this->add( 'join', new Expr\Join( Expr\Join::INNER_JOIN, $join, $alias, $conditionType, $condition ), true );
	}
	
	/**
	 * Creates and adds a left join over an entity association to the query.
	 *
	 * The entities in the joined association will be fetched as part of the query
	 * result if the alias used for the joined association is placed in the select
	 * expressions.
	 *
	 * <code>
	 * $qb = $em->createQueryBuilder()
	 * ->select('u')
	 * ->from('User', 'u')
	 * ->leftJoin('u.Phonenumbers', 'p', Expr\Join::WITH, 'p.is_primary = 1');
	 * </code>
	 *
	 * @param string $join The relationship to join
	 * @param string $alias The alias of the join
	 * @param string $conditionType The condition type constant. Either ON or WITH.
	 * @param string $condition The condition for the join
	 * @return QueryBuilder This QueryBuilder instance.
	 */
	public function leftJoin($join, $alias, $conditionType = null, $condition = null) {
		return $this->add( 'join', new Expr\Join( Expr\Join::LEFT_JOIN, $join, $alias, $conditionType, $condition ), true );
	}
	
	/**
	 * Sets a new value for a field in a bulk update query.
	 *
	 * <code>
	 * $qb = $em->createQueryBuilder()
	 * ->update('User', 'u')
	 * ->set('u.password', md5('password'))
	 * ->where('u.id = ?');
	 * </code>
	 *
	 * @param string $key The key/field to set.
	 * @param string $value The value, expression, placeholder, etc.
	 * @return QueryBuilder This QueryBuilder instance.
	 */
	public function set($key, $value) {
		return $this->add( 'set', new Expr\Comparison( $key, Expr\Comparison::EQ, $value ), true );
	}
	
	/**
	 * Specifies one or more restrictions to the query result.
	 * Replaces any previously specified restrictions, if any.
	 *
	 * <code>
	 * $qb = $em->createQueryBuilder()
	 * ->select('u')
	 * ->from('User', 'u')
	 * ->where('u.id = ?');
	 *
	 * // You can optionally programatically build and/or expressions
	 * $qb = $em->createQueryBuilder();
	 *
	 * $or = $qb->expr()->orx();
	 * $or->add($qb->expr()->eq('u.id', 1));
	 * $or->add($qb->expr()->eq('u.id', 2));
	 *
	 * $qb->update('User', 'u')
	 * ->set('u.password', md5('password'))
	 * ->where($or);
	 * </code>
	 *
	 * @param mixed $predicates The restriction predicates.
	 * @return QueryBuilder This QueryBuilder instance.
	 */
	public function where($predicates) {
		if( !(func_num_args() == 1 && ($predicates instanceof Expr\Andx || $predicates instanceof Expr\Orx)) ) {
			$predicates = new Expr\Andx( func_get_args() );
		}
		
		return $this->add( 'where', $predicates );
	}
	
	/**
	 * Adds one or more restrictions to the query results, forming a logical
	 * conjunction with any previously specified restrictions.
	 *
	 * <code>
	 * $qb = $em->createQueryBuilder()
	 * ->select('u')
	 * ->from('User', 'u')
	 * ->where('u.username LIKE ?')
	 * ->andWhere('u.is_active = 1');
	 * </code>
	 *
	 * @param mixed $where The query restrictions.
	 * @return QueryBuilder This QueryBuilder instance.
	 * @see where()
	 */
	public function andWhere($where) {
		$where = $this->getDQLPart( 'where' );
		$args = func_get_args();
		
		if( $where instanceof Expr\Andx ) {
			$where->addMultiple( $args );
		} else {
			array_unshift( $args, $where );
			$where = new Expr\Andx( $args );
		}
		
		return $this->add( 'where', $where, true );
	}
	
	/**
	 * Adds one or more restrictions to the query results, forming a logical
	 * disjunction with any previously specified restrictions.
	 *
	 * <code>
	 * $qb = $em->createQueryBuilder()
	 * ->select('u')
	 * ->from('User', 'u')
	 * ->where('u.id = 1')
	 * ->orWhere('u.id = 2');
	 * </code>
	 *
	 * @param mixed $where The WHERE statement
	 * @return QueryBuilder $qb
	 * @see where()
	 */
	public function orWhere($where) {
		$where = $this->getDqlPart( 'where' );
		$args = func_get_args();
		
		if( $where instanceof Expr\Orx ) {
			$where->addMultiple( $args );
		} else {
			array_unshift( $args, $where );
			$where = new Expr\Orx( $args );
		}
		
		return $this->add( 'where', $where, true );
	}
	
	/**
	 * Specifies a grouping over the results of the query.
	 * Replaces any previously specified groupings, if any.
	 *
	 * <code>
	 * $qb = $em->createQueryBuilder()
	 * ->select('u')
	 * ->from('User', 'u')
	 * ->groupBy('u.id');
	 * </code>
	 *
	 * @param string $groupBy The grouping expression.
	 * @return QueryBuilder This QueryBuilder instance.
	 */
	public function groupBy($groupBy) {
		return $this->add( 'groupBy', new Expr\GroupBy( func_get_args() ) );
	}
	
	/**
	 * Adds a grouping expression to the query.
	 *
	 * <code>
	 * $qb = $em->createQueryBuilder()
	 * ->select('u')
	 * ->from('User', 'u')
	 * ->groupBy('u.lastLogin');
	 * ->addGroupBy('u.createdAt')
	 * </code>
	 *
	 * @param string $groupBy The grouping expression.
	 * @return QueryBuilder This QueryBuilder instance.
	 */
	public function addGroupBy($groupBy) {
		return $this->add( 'groupBy', new Expr\GroupBy( func_get_args() ), true );
	}
	
	/**
	 * Specifies a restriction over the groups of the query.
	 * Replaces any previous having restrictions, if any.
	 *
	 * @param mixed $having The restriction over the groups.
	 * @return QueryBuilder This QueryBuilder instance.
	 */
	public function having($having) {
		if( !(func_num_args() == 1 && ($having instanceof Expr\Andx || $having instanceof Expr\Orx)) ) {
			$having = new Expr\Andx( func_get_args() );
		}
		
		return $this->add( 'having', $having );
	}
	
	/**
	 * Adds a restriction over the groups of the query, forming a logical
	 * conjunction with any existing having restrictions.
	 *
	 * @param mixed $having The restriction to append.
	 * @return QueryBuilder This QueryBuilder instance.
	 */
	public function andHaving($having) {
		$having = $this->getDqlPart( 'having' );
		$args = func_get_args();
		
		if( $having instanceof Expr\Andx ) {
			$having->addMultiple( $args );
		} else {
			array_unshift( $args, $having );
			$having = new Expr\Andx( $args );
		}
		
		return $this->add( 'having', $having );
	}
	
	/**
	 * Adds a restriction over the groups of the query, forming a logical
	 * disjunction with any existing having restrictions.
	 *
	 * @param mixed $having The restriction to add.
	 * @return QueryBuilder This QueryBuilder instance.
	 */
	public function orHaving($having) {
		$having = $this->getDqlPart( 'having' );
		$args = func_get_args();
		
		if( $having instanceof Expr\Orx ) {
			$having->addMultiple( $args );
		} else {
			array_unshift( $args, $having );
			$having = new Expr\Orx( $args );
		}
		
		return $this->add( 'having', $having );
	}
	
	/**
	 * Specifies an ordering for the query results.
	 * Replaces any previously specified orderings, if any.
	 *
	 * @param string $sort The ordering expression.
	 * @param string $order The ordering direction.
	 * @return QueryBuilder This QueryBuilder instance.
	 */
	public function orderBy($sort, $order = null) {
		return $this->add( 'orderBy', $sort instanceof Expr\OrderBy ? $sort : new Expr\OrderBy( $sort, $order ) );
	}
	
	/**
	 * Adds an ordering to the query results.
	 *
	 * @param string $sort The ordering expression.
	 * @param string $order The ordering direction.
	 * @return QueryBuilder This QueryBuilder instance.
	 */
	public function addOrderBy($sort, $order = null) {
		return $this->add( 'orderBy', new Expr\OrderBy( $sort, $order ), true );
	}
	
	/**
	 * Get a query part by its name.
	 *
	 * @param string $queryPartName
	 * @return mixed $queryPart
	 * @todo Rename: getQueryPart (or remove?)
	 */
	public function getDQLPart($queryPartName) {
		return $this->_dqlParts[$queryPartName];
	}
	
	/**
	 * Get all query parts.
	 *
	 * @return array $dqlParts
	 * @todo Rename: getQueryParts (or remove?)
	 */
	public function getDQLParts() {
		return $this->_dqlParts;
	}
	
	private function _getDQLForDelete() {
		return 'DELETE' . $this->_getReducedDQLQueryPart( 'from', array( 'pre' => ' ', 'separator' => ', ' ) ) . $this->_getReducedDQLQueryPart( 'where', array( 'pre' => ' WHERE ' ) ) . $this->_getReducedDQLQueryPart( 'orderBy', array( 'pre' => ' ORDER BY ', 'separator' => ', ' ) );
	}
	
	private function _getDQLForUpdate() {
		return 'UPDATE' . $this->_getReducedDQLQueryPart( 'from', array( 'pre' => ' ', 'separator' => ', ' ) ) . $this->_getReducedDQLQueryPart( 'set', array( 'pre' => ' SET ', 'separator' => ', ' ) ) . $this->_getReducedDQLQueryPart( 'where', array( 'pre' => ' WHERE ' ) ) . $this->_getReducedDQLQueryPart( 'orderBy', array( 'pre' => ' ORDER BY ', 'separator' => ', ' ) );
	}
	
	private function _getDQLForSelect() {
		return 'SELECT' . $this->_getReducedDQLQueryPart( 'select', array( 'pre' => ' ', 'separator' => ', ' ) ) . $this->_getReducedDQLQueryPart( 'from', array( 'pre' => ' FROM ', 'separator' => ', ' ) ) . $this->_getReducedDQLQueryPart( 'join', array( 'pre' => ' ', 'separator' => ' ' ) ) . $this->_getReducedDQLQueryPart( 'where', array( 'pre' => ' WHERE ' ) ) . $this->_getReducedDQLQueryPart( 'groupBy', array( 'pre' => ' GROUP BY ', 'separator' => ', ' ) ) . $this->_getReducedDQLQueryPart( 'having', array( 'pre' => ' HAVING ' ) ) . $this->_getReducedDQLQueryPart( 'orderBy', array( 'pre' => ' ORDER BY ', 'separator' => ', ' ) );
	}
	
	private function _getReducedDQLQueryPart($queryPartName, $options = array()) {
		$queryPart = $this->getDQLPart( $queryPartName );
		
		if( empty( $queryPart ) ) {
			return (isset( $options['empty'] ) ? $options['empty'] : '');
		}
		
		return (isset( $options['pre'] ) ? $options['pre'] : '') . (is_array( $queryPart ) ? implode( $options['separator'], $queryPart ) : $queryPart) . (isset( $options['post'] ) ? $options['post'] : '');
	}
	
	/**
	 * Reset DQL parts
	 *
	 * @param array $parts
	 * @return QueryBuilder
	 */
	public function resetDQLParts($parts = null) {
		if( is_null( $parts ) ) {
			$parts = array_keys( $this->_dqlParts );
		}
		foreach( $parts as $part ) {
			$this->resetDQLPart( $part );
		}
		return $this;
	}
	
	/**
	 * Reset single DQL part
	 *
	 * @param string $part
	 * @return QueryBuilder;
	 */
	public function resetDQLPart($part) {
		if( is_array( $this->_dqlParts[$part] ) ) {
			$this->_dqlParts[$part] = array();
		} else {
			$this->_dqlParts[$part] = null;
		}
		$this->_state = self::STATE_DIRTY;
		return $this;
	}
	
	/**
	 * Gets a string representation of this QueryBuilder which corresponds to
	 * the final DQL query being constructed.
	 *
	 * @return string The string representation of this QueryBuilder.
	 */
	public function __toString() {
		return $this->getDQL();
	}
	
	/**
	 * Deep clone of all expression objects in the DQL parts.
	 *
	 * @return void
	 */
	public function __clone() {
		foreach( $this->_dqlParts as $part => $elements ) {
			if( is_array( $this->_dqlParts[$part] ) ) {
				foreach( $this->_dqlParts[$part] as $idx => $element ) {
					if( is_object( $element ) ) {
						$this->_dqlParts[$part][$idx] = clone $element;
					}
				}
			} else if( is_object( $elements ) ) {
				$this->_dqlParts[$part] = clone $elements;
			}
		}
	}
}